An image forming apparatus includes a plurality of paper feed cassettes. The image forming apparatus sets a sheet size which is different for each cassette and determines a cassette from which sheets are fed according to a sheet size designated in a job.
To the contrary, there is another type of image forming apparatus which sets a same sheet size for a plurality of cassettes and is capable of continuing to feed sheets from another cassette when one cassette runs out of sheets during execution of a job. For example, the image forming apparatus set A4-size for two cassettes of a first cassette and a second cassette as the size of the sheets. When the image forming apparatus executes a job of printing A4-size sheets, the image forming apparatus starts printing of A4-size sheets from the first cassette and then continues to feed sheets from the second cassette when the first cassette runs out of sheets during the printing. This function is referred to as an automatic switching function.
Meanwhile, there is a system that carries out a decoloring process so that a sheet can be reused, when a decolorable image is formed on the sheet by an image forming apparatus and the image is no longer needed.
Here, it is assumed that image formation using a decolorable toner is carried out on a plurality of sheets and then the sheets are bundled by stapling the sheets according to a job. When the bundled sheets are no longer needed and a decoloring process is performed on the sheets that are unbundled using a decoloring device, a folded portion or the like is frequently formed in the stapled portions. Further, bundled sheets on which an image is formed using a decolorable toner and which was subjected to post-processing such as a punching process (punching) or a center folding process (process of bundling sheets and folding the central portion thereof) is not suitable for reuse because punched holes or folded portions exist in the sheets.
Sheets (successfully) subjected to the decoloring process (hereinafter, referred to as reuse sheets) may include sheets which have been subjected to a printing process plural times and have a plurality of toner layers stacked thereon. Since the reuse sheets are sheets on which the printing process and the decoloring process are performed at least once, respectively, the sheets may not be in an excellent state. When post-processing is performed on such sheets, the positions of holes made through the punching may be shifted, and the sheets are not aligned properly during the stapling. As a result, the post-processing may not be carried out precisely.
In light of the above, the following situation is assumed. That is, in an image forming apparatus having the automatic switching function, a first cassette stores new sheets and a second cassette stores reuse sheets of the same size as the new sheets, and the image forming apparatus executes a printing job including post-processing. The reuse sheets from the second cassette are used when the first cassette runs out of new sheets during execution of the job and the first cassette is switched to the second cassette according to the automatic switching function. Since the precision of the post-processing is decreased for the reason as described above when reuse sheets are used, a sheet bundle (document) created as a result may not be in a best quality.